Not without some serious dock connector/PDS hacking - even then, maybe not. For starters, it's highly doubtful you can even make, let alone find, anything resembling the PPC PDS inside the Dock or on the docking connector - more likely something like an '030 or LC PDS held over from the 68k Duo designs.
ISTR that the Nubus riser board appears to the system as a PDS; the FPU socket might be another point of interest. Is there even a cache socket in any of the Docks? Either way, this sounds like a major engineering project.
Paging Trash80toG4 ... where is that guy?? A Duo that becomes a G3 when docked would be right up his alley, let alone mine. }
Not so - Rockets with the right software version will work quite happily in x100 Nubus PPCs - and thus, by implication, in a 2300/Dock. A 40MHz Stage II should indeed give the 100MHz PPC a fair run for its money with 68k code.